Power saving support for wireless networks

ABSTRACT

Various example embodiments are disclosed. According to an example embodiment, a technique may include transmitting a scheduling information to a mobile station in a wireless network during a listening window, determining whether an acknowledgement has been received within the listening window from the mobile station that acknowledges receipt of the scheduling information, resetting a size of a next sleep window for the mobile station to an initial sleep window size if the acknowledgement has been received from the mobile station, and increasing a size of the next sleep window for the mobile station if the acknowledgement has not been received from the mobile station within the listening window. In another example embodiment, techniques are disclosed for determining a starting location of a next listening window for a mobile station in a wireless network.

TECHNICAL FIELD

This description relates to wireless networks.

BACKGROUND

In some wireless networks, mobile stations (or subscriber stations) mayoccasionally switch to a low power or sleep mode. For example, a mobilestation (MS) may negotiate with a base station (BS) to temporarilydisrupt one or more wireless connections between the MS and the BS for aperiod of time known as a sleep window (which may last one or moreframes, for example). During the sleep window, the BS does not scheduleany downlink (DL) transmissions to the MS and the MS does not send anyuplink (UL) transmissions to the BS, so that the MS may power down oneor more hardware components required for communication in order toconserve power during the sleep window. For example, during a sleepwindow for a MS, the BS may buffer or drop arriving unicast packetsassociated with the MS (or associated with the MS's connection ID oruser ID or MS ID), and may buffer any multicast packets for multicasttransmission associated with a multicast ID for which the sleeping MS isa member. Each sleep window may typically be followed by a listeningwindow in which the MS returns power to its required hardware componentsfor communication and restores its one or more connections with the BS.During the listening window, any data buffered by the BS for the MS maythen be transmitted to the MS and the MS may transmit UL to the BS. TheMS may alternate between sleep and listening windows.

SUMMARY

According to an example embodiment, a method may include transmitting ascheduling information to a mobile station in a wireless network duringa listening window, determining whether an acknowledgement has beenreceived within the listening window from the mobile station thatacknowledges receipt of the scheduling information, resetting a size ofa next sleep window for the mobile station to an initial sleep windowsize if the acknowledgement has been received from the mobile station,and increasing a size of the next sleep window for the mobile station ifthe acknowledgement has not been received from the mobile station withinthe listening window.

According to another example embodiment, an apparatus may include awireless transceiver; and a controller coupled to the transceiver. Thewireless transceiver may be configured to transmit a schedulinginformation to a mobile station in a wireless network during a listeningwindow. The controller may be configured to determine whether anacknowledgement has been received within the listening window from themobile station that acknowledges receipt of the scheduling information,reset a size of a next sleep window for the mobile station to an initialsleep window size if the acknowledgement has been received from themobile station, and increase a size of the next sleep window for themobile station if the acknowledgement has not been received from themobile station within the listening window.

According to another example embodiment, a method may includetransmitting a scheduling information to a mobile station in a wirelessnetwork during a listening window, determining that an acknowledgementhas been received within the listening window from the mobile stationthat acknowledges receipt of the scheduling information, and, resettinga size of a next sleep window for the mobile station to an initial sleepwindow size based on the receipt of the acknowledgement.

According to another example embodiment, an apparatus may include awireless transceiver and a controller coupled to the transceiver. Thewireless transceiver may be configured to transmit a schedulinginformation to a mobile station in a wireless network during a listeningwindow. The controller may be configured to: determine that anacknowledgement has been received within the listening window from themobile station that acknowledges receipt of the scheduling information,and reset a size of a next sleep window for the mobile station to aninitial sleep window size based on the receipt of the acknowledgement.

According to another example embodiment may include receiving, at amobile station from a base station in a wireless network during alistening window, a scheduling information that assigns or allocatesresources to the mobile station for either uplink or downlinktransmission, transmitting, within the listening window, anacknowledgement from the mobile station that acknowledges receipt of thescheduling information, and resetting a size of a next sleep window forthe mobile station to an initial sleep window size based on the receiptof the scheduling information for the mobile station.

According to another example embodiment a method may include determininga starting location of a next listening window for a mobile station in awireless network, communicating traffic between the mobile station and abase station during a current listening window, determining, based onthe communicating, an extension (m) of the current listening window,determining a length of a next sleep window based on the extension (m)of the current listening window and an initial sleep window size (t),and, determining a starting location of the next listening window basedon the starting point (n) of the current listening window, a length (v)of an unextended listening window, the extension (m) of the currentlistening window and the initial sleep window size (t).

According to another example embodiment, a method of determining astarting location of a next listening window for a mobile station in awireless network may include receiving, from a base station, traffic atthe mobile station during a current listening window, determining, basedon the receiving, an extension (m) of the current listening window, anddetermining a starting location of the next listening window based onthe starting point (n) of the current listening window, a length (v) ofan unextended listening window, the extension (m) of the currentlistening window and the initial sleep window size (t).

According to an example embodiment, an apparatus may include a wirelesstransceiver and a controller coupled to the transceiver. The wirelesstransceiver may be configured to receive, from a base station, trafficat the mobile station during a current listening window. The controllermay be configured to determine an extension (m) of the current listeningwindow; and determine a starting location of the next listening windowbased on the starting point (n) of the current listening window, alength (v) of an unextended listening window, the extension (m) of thecurrent listening window and the initial sleep window size (t).

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features will beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless network according to an exampleembodiment.

FIG. 2 is a diagram illustrating a frame structure 210 according to anexample embodiment.

FIG. 3 is a block diagram illustrating operation of a mobile stationaccording to an example embodiment.

FIG. 4 is a timing diagram that illustrates operation according to anexample embodiment.

FIG. 5 is a diagram illustrating operation of a wireless node in a casewhere the extension (m) of the current listening window is less than theinitial sleep window size (t).

FIG. 6 is a diagram illustrating operation of a wireless node in a casewhere the extension (m) of the current listening window is greater thanor equal to the initial sleep window size (t).

FIG. 7 is a flow chart illustrating operation of a base stationaccording to an example embodiment.

FIG. 8 is a flow chart illustrating operation of a base stationaccording to an example embodiment.

FIG. 9 is a flow chart illustrating operation of a mobile stationaccording to an example embodiment.

FIG. 10 is a flow chart illustrating operation of a wireless nodeaccording to an example embodiment.

FIG. 11 is a flow chart illustrating operation of a mobile stationaccording to an example embodiment.

FIG. 12 is a block diagram of a wireless node according to an exampleembodiment.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a wireless network 102 including a basestation 104 and three mobile stations 106, 108, 110 according to anexample embodiment. While only three mobile stations are shown, anynumber may be provided. Although not shown, mobile stations 106, 108 and110 may be coupled to base station 104 via relay stations or relaynodes, for example. The wireless network 102 may include, for example,an IEEE 802.16 Worldwide interoperability for Microwave Access (WiMAX)network, an IEEE 802.11 Wireless Local Area Network (WLAN) network, acellular telephone network, or other wireless network, according toexample embodiments. The base station 104 may include a cellular orWiMAX base station (BS), a node B, an 802.11 access point, or otherinfrastructure node, according to various example embodiments. The term“base station” (BS) may be used herein and may include any type ofinfrastructure node. The mobile stations 106, 108, 110 may includelaptop or notebook computers, smartphones, personal digital assistants(PDAs), cellular telephones, WiMAX device, subscriber station, or anyother wireless device, according to example embodiments. The term“wireless node” (or “wireless station”) may include any type of wirelessnode, such as base stations, mobile stations, relay stations, etc. Whilethe present disclosure may use some of the terminology of WiMAX or otherwireless standards or specifications, the present disclosure may beapplicable to any networking or wireless technologies. Base station (BS)104 may transmit information (e.g., either broadcast, multicast orunicast) in a downlink (DL) direction to each mobile station (MS) 106,108, 110, and each MS 106, 108, 110 may transmit information to the BS104 in an uplink (UL) direction.

FIG. 2 is a diagram illustrating a frame structure 210 according to anexample embodiment. As shown in FIG. 2, several superframes are shown,including superframe 0, superframe 1, superframe 2, superframe 3, . . .. Each superframe may include a number of frames, such as, for example,four frames per superframe. Each frame may include a number ofsubframes, such as, for example, eight subframes per frame. For example,as shown, frame 1 may include eight subframes, such as subframes 0-7.Thus, according to an example embodiment, a superframe may include 32subframes, although any number of subframes may be used. Each subframemay include transmission resources, such as, for example, a number ofOrthogonal Frequency Division Multiplexing (OFDM) symbols, e.g., acrossone or more subcarriers. For example, each subframe may include 5-7 OFDMsymbols, depending on a type of the subframe. These are merely examples,and a subframe may include any number of resources or OFDM symbols.

Each subframe may be allocated by BS 104 for either DL transmission orUL transmission. The DL/UL ratio for subframes within a frame may vary,based on control information indicated or transmitted by the BS 104. Forexample, the DL/UL ratio may be 4/4 (meaning, the frame includes 4 DLsubframes followed by 4 UL subframes), may be 5/3, or 3/5 or otherratio, depending on the UL and DL traffic in the network. For example,one or more DL subframes may occur first in a frame for the BS 104 totransmit broadcast and unicast information to MSs, followed by one ormore UL subframes that may allow one or more of the MSs opportunities orresources to transmit UL to the BS 104.

Referring to FIG. 2 again, the first subframe (subframe 0 in FIG. 2) ofeach superframe is typically allocated for downlink transmission. Eachsuperframe may include a superframe header (SFH) that is included in thefirst subframe of the superframe (subframe 0) of the first frame (frame0) of the superframe. The SFH may include a number of fields, includinga broadcast channel (BCH) 212. The BCH 212 may be used by the BS 104 tobroadcast to all MSs or provide essential system parameters and systemconfiguration information 214. The BCH 212 may include a primarybroadcast channel (PBCH) and a secondary broadcast channel (SBCH). ThePBCH may carry deployment wide (or network wide) common information fromthe BS, while the SBCH may carry sector specific information, where MSsin wireless network 102 may be divided into different sectors. In anexample embodiment, the BCH 212 may be frequency division multiplexedwith data within the same subframe (subframe 0).

As noted, BCH 212, e.g., provided within a first subframe of asuperframe, may include system configuration information 214. Systemconfiguration information 214 may include or describe the systemconfiguration of one or more (or each) of the subframes of a superframe.In some cases, the system configuration information 214 may beconsidered essential for decoding subframes. System configurationinformation 214 may include, for example, DL/UL ratio for subframeswithin the superframe (e.g., first 5 subframes are for DL, and last 3subframes are for UL), subframe concatenation pattern for a superframe,the configuration information of localized resource allocations (LRAs)and distributed resource allocations (DRAs) within a subframe (which mayallocate resources for UL or DL transmissions), permutation method forsubcarriers, and/or other system configuration information.

As shown in FIG. 2, each subframe may include other data and controlinformation. Although, FIG. 2 only shows the other data and controlinformation for subframe 0, each subframe may include other data andcontrol information. For example, each subframe may include schedulinginformation that may schedule, assign or allocate resources to each ofthe MSs for UL or DL transmissions. The scheduling information in asubframe may allocate or assign resources to a MS for the same subframe,or a future subframe, as examples.

In an example embodiment, the scheduling information may be provided in(or as part of) a unicast service control channel or a Map message.These are merely some examples, and the scheduling information may beprovided in a number of different formats, or may be known by differentnames. The scheduling information may include, for example, MS-specific(e.g., user-specific or connection-specific) scheduling assignments toassign or allocate UL or DL resources to different MSs. The schedulingassignments may be for unicast transmissions (either uplink ordownlink), or DL multicast or broadcast transmissions (e.g., where a MSmay be a member of one or more multicast groups).

For example, the MS-specific scheduling information that identifies ULresources for a MS may identify UL resources (e.g., time slot and/orsubcarriers or other resources) assigned or allocated to the MS to allowthe MS an opportunity to transmit UL to the BS, e.g., in a same ordifferent subframe of the same frame or a next frame, as examples.Similarly, the MS-specific scheduling information that assigns DLresources to a MS may identify resources (e.g., time slot and/orsubcarriers) within a current subframe or a future subframe (e.g., nextsubframe) for which the BS will transmit data to the MS. Thus, duringsuch time period specified by the scheduling assignment or resourceallocation, the MS should typically be in a non-sleep (or active) modeor listening window so that the MS may receive the data via thedesignated resources. Otherwise, if the MS is in sleep window duringthis period, the BS may transmit data (or other information) to thesleeping MS, and the data or other information may be lost (not receivedby the MS), for example.

FIG. 3 is a block diagram illustrating operation of a mobile stationaccording to an example embodiment. In an example embodiment, a MS(mobile station) may alternate between a listening window, where the MSmay receive data and may transmit data, and a sleep window, where the MSmay power down one or more components such that the MS is unable toreceive or transmit data, and the BS (base station) typically does nottransmit data to the MS during a sleep mode. Each sleep window andlistening window may be one or more frames, for example. The length ofeach sleep window or listening window may be specified by the BS, or maybe negotiated between the MS and BS, as examples. For example, as shownin FIG. 3, a MS may initially operate in a listening window 310, then ina sleep window 312, then a listening window 314, and then a sleep window316, etc.

According to an example embodiment, a MS may use an initial sleep windowsize. If there is no traffic (e.g., data and/or control information)exchanged between the MS and BS during a next listening window, then thesize of the following (or next) sleep window may be increased to allowfor greater power savings. For example, if a MS has an initial sleepwindow size of 3 frames assigned to it by the BS, then, e.g., if notraffic is exchanged between the MS and BS in the next listening window,then the following or next sleep window may be doubled to 6 frames(e.g., 2 times the initial sleep window size). Each sleep window may beincreased (e.g., doubled) if there was no MS-specific traffic sent tothe MS or received from the MS during the previous listening window.Thus, if no MS-specific traffic occurs in each listening window, theneach sleep window may double, e.g., 3 frames (the initial sleep windowsize), 6 frames (2× initial sleep window size), 12 frames (4× initialsleep window size), etc., up to a maximum sleep window size.Alternatively, each sleep window size may increase to a higher multipleof the initial sleep window size, e.g., 2× (two times the initial sleepwindow size), 3×, 4×, 5×, 6×, . . . up to a maximum sleep window size.According to an example embodiment, if MS-specific traffic (e.g.,traffic or packets transmitted to or addressed to the MS, or receivedfrom the MS) occurs during a listening window, then the next sleepwindow is reset to the initial sleep window size (3 frames in the aboveexample).

According to an example embodiment, both the BS and the MS may eitherincrease the size of the next sleep window, or reset the size of thenext sleep window to the initial sleep window size, depending on whetherMS-specific traffic occurs in the previous listening window. Accordingto an example embodiment, one way to determine whether MS-specifictraffic occurs within a listening window is whether the BS allocates orassigns UL or DL resources for the MS (MS-specific resource allocation),e.g., by transmission of scheduling information. Thus, if the BStransmits scheduling information to a MS during a subframe within alistening window, this may, for example, allocate or identify either DLresources for the BS to transmit to the MS, or allocate UL resources toallow the MS to transmit to the BS. In such case, e.g., based on thescheduling information (or based on the allocation of resources to theMS via the scheduling information) both the MS and the BS should resetthe size of the next sleep window for the MS to the initial sleep windowsize. Different MSs may have different sleep windows and listeningwindows.

However, a problem can arise where the BS transmits schedulinginformation (e.g., for a subframe within a listening window) to a MS,but the MS does not receive the scheduling information, e.g., the MS isunable to decode the scheduling information due to signal errors, a deepfade of the received signal, or other problem. In such case, the BS mayreset the size of the next sleep window to the initial sleep windowsize. However, since the MS did not receive the scheduling informationfor the MS (and therefore, may typically be unaware of any data to betransmitted to the MS via the allocated resources), the MS may thenincrease (e.g., double) the size of its next sleep window. Thus, as aresult, the MS and BS will determine two different sizes for the nextsleep window for the MS. This will cause the MS and BS to identify twodifferent starting points for the next listening window (at the end ofthe next sleep window). As a result, the MS may lose synchronizationwith the BS, since the BS may then transmit scheduling information (ordata) to the MS while the MS is in sleep mode (since the MS increasedthe size of the next sleep window, while the BS may have typicallydecreased the sleep window size by resetting it based on thetransmission of the scheduling information to the MS). As a result ofthis loss of synchronization, and the MS may be required to performnetwork re-entry (to re-obtain synchronization with the BS), likelycausing a service interruption for the MS.

Therefore according to an example embodiment, a MS may transmit to theBS an acknowledgement to acknowledge receipt of a schedulinginformation. FIG. 4 is a timing diagram that illustrates operationaccording to an example embodiment. A listening window 410 is shown. At412, BS 104 transmits scheduling information to the MS 106. Thescheduling information may, for example, include a Map message or ascheduling assignment, or other resource allocation, to allocate UL orDL resources to the MS. At 412, the BS may also transmit a signal orinformation element (e.g., Map IE or Ack Request IE) that requests theMS to send an acknowledgement to the BS via an allocated Ack channel,for example. This may allow the BS to notify the MS of cases where theMS should send an acknowledgement to the BS. At 412, the BS may alsotransmit a scheduling resource that allocates resources for the MS totransmit the acknowledgement. These allocated resources for theacknowledgement may be referred to as the acknowledgement channel, forexample.

At 414 the MS 106 transmits (or sends) an acknowledgement to the BS 104.The acknowledgement may be sent, e.g., in response to receiving thescheduling information and/or in response to receiving a request for theacknowledgement, and may be sent to the BS via the allocated or reservedacknowledgement channel, according to example embodiments, although notrequired.

At 420, in response to receiving/decoding the scheduling information(that allocates resources to the MS), the MS 106 resets (or adjusts) thenext sleep window 422 for the MS to the initial sleep window size.Likewise, at 418, after receiving the acknowledgement from MS 106 (via44), the BS 104 resets (or adjusts) the size of the next sleep window422 for the MS to the initial sleep window size. Thus, the use of theacknowledgement (at 414) sent from the MS 106 to the BS 104 may decreasethe likelihood for a miscommunication between the BS and MS with respectto the size of the next sleep window (e.g., which may result in the MSand BS determining different sleep window sizes, which may typicallycause the MS and BS to become unsynchronized).

Although not required, according to an example embodiment, if the BS 104does not receive the acknowledgement (at 414), e.g., after a timeoutafter sending the scheduling information to the MS, the BS may repeat,one or more times, transmitting a scheduling information to the MS,until either the BS receives an acknowledgement from the MS (e.g., viaan allocated Ack channel) or the end of the current listening window 410is reached. For example, the BS may send scheduling resources in eachsubframe within listening window 410, and may include an Ack request IE(requesting an acknowledgement) and/or allocate or provide anacknowledgment channel for the scheduling information of the firstsubframe, and then if no acknowledgement is received, then the BS mayinclude an Ack request IE and allocated Ack channel for the secondsubframe of the listening window 410, and if no acknowledgement isreceived by the BS for that request, then the BS may provide the Ackrequest IE and Ack channel for the third subframe, etc. until either anacknowledgement is received at the BS or the end of the listening windowis received.

In an example embodiment, after an Ack (acknowledgement) has beenreceived by the BS for a scheduling resource (and/or in response to anAck request), the BS may typically not include a Ack request IE(requesting an acknowledgement) or allocate an Ack channel forsubsequent or further transmissions of scheduling resources within thesame listening window 410 (since the BS has already been notified thatthe MS is aware of MS-specific traffic for this listening window, whichmeans that the MS will reset size of next sleep window 422 to theinitial sleep window size based on the occurrence of MS-specific trafficwithin listening window 410).

If BS 104 does not receive an acknowledgement by the end of thelistening window 410, the BS 104 may assume that the MS 106 has notreceived the scheduling information, and the BS 106 may then increasethe size of the next sleep window 422 (e.g., because it may be assumedbased on the failure to received the Ack that the MS did not receive thescheduling information, and as a result, the MS will likely increase thesize of its next sleep window). Thus, in such case, to keep the BS andMS synchronized, the BS will also increase the size of the next sleepwindow 422 for the MS.

At 416, the MS and BS may exchange data via the allocated UL and/or DLresources. This may include, for example, the BS transmitting data (orother signals) to the BS via DL resources indicated by the schedulinginformation that was sent to the MS, or may include the MS sending dataor other signals to the BS via allocated UL resources (indicated by thescheduling information for example).

According to an example embodiment, the MS may be required toacknowledge only one scheduling information received within a listeningwindow. For example, a scheduling information (e.g., Map message orunicast service control channel) may be provided within each of one ormore subframes within a listening window. The BS may, for example,allocate an acknowledgement channel to allow the MS to acknowledgereceipt of the scheduling information for one of the subframes, e.g.,for the first subframe, or subframe 0, according to an exampleembodiment. For example, any subframe within a listening window may beselected to request the acknowledgement/or allocate an Ack channel.

In an example embodiment, the MS may send an acknowledgement in responseto receiving a DL resource allocation within a listening window. If a MSreceived an UL resource allocation (to allow the MS to transmit to theMS, the BS may be notified of the MS's receipt of the UL resourceallocation (scheduling information including the UL resource allocation)when the MS uses the UL resource allocation to transmit data or othersignal to the BS, for example. Thus, in the case where a listeningwindow includes the BS transmitting a scheduling information thatprovides an UL resource allocation to the MS, it may not be necessaryfor the MS to acknowledge this scheduling information since the MS willimplicitly acknowledge receipt of such scheduling information bytransmitting data or other signal to the BS via the allocated ULresource, for example. Thus, according to an example embodiment, the MSmay acknowledge receipt of a scheduling information that provides a DLresource allocation within a listening window, e.g., where the MS is notusing an allocated UL resource allocation to transmit to the BS withinthe same window. Thus, for example, in an example embodiment, it may bedesirable for the MS to explicitly acknowledge receipt of a schedulinginformation for a DL resource allocation where the MS does not receiveor respond to a UL resource allocation within the same listening window,according to an example embodiment. This is because, for example,receipt at the BS of an UL transmission from the MS (e.g., in responseto an UL allocation) within a listening window 410 indicates to the BSthat the MS will reset the size of its next sleep window 422 to theinitial sleep window size.

In an example embodiment, it may be unnecessary to acknowledge thescheduling information if HARQ (Hybrid ARQ) transmission mode is usedfor the BS to send data to the MS, since, for example, a HARQ Ack/Nakchannel may provide the MS with a channel to acknowledge or negativelyacknowledge receipt of the data (and hence, providing an indication ornot, of whether the MS will reset or increase the size of the next sleepwindow 422). Thus, according to an example embodiment, theacknowledgement described above may be especially useful where the BStransmits data to the MS via a non-HARQ (non-Hybrid ARQ) transmission.

According to an example embodiment a listening window may be extended,e.g., by one or more frames to accommodate traffic or increased trafficduring the listening window. The amount of extension (m) added to thecurrent listening window may be a fixed (or selected or configurable)extension amount (m), which may be applied to extend the currentlistening window, e.g., if there is any traffic in the unextendedportion of the listening window or traffic that exceeds a threshold, asexamples. The amount of the extension (m) may be selected by the BS(e.g., in advance) and then the BS may notify the MS of the extensionamount, which may be applied by both the MS and BS if a condition isfulfilled, e.g., traffic (or a threshold amount of traffic) occurswithin the un-extended listening window, for example.

Alternatively the current listening window may be flexibly extended byan amount (m) based on (or in accordance with) an amount of trafficoccurring or communicated between the BS and MS during the currentlistening window. For example, the MS and BS may exchange traffic duringthe listening interval. The listening window may be extended as long asthere is DL or UL data traffic between the MS and BS. Once the listeningwindow is entered (or has started), a timer (set to an initial value) isstarted (e.g., decrementing), and the timer is reset if any trafficreception/transmission is performed. If the timer expires (e.g., due tono additional traffic at that point between MS and BS), the listeningwindow is not further extended and the MS may enter sleep mode until thenext scheduled listening window. This is merely another example, and theamount of the extension (m) of the listening window may be determined orcalculated using a number of different techniques, as these are just afew possible techniques to determine an extension (m) to the listeningwindow, and the disclosure is not limited thereto.

When the current listening window is extended, this may typically changethe starting point and length of the next sleep window, and as a result,may change a starting location of a next listening window. The startinglocation of the next listening window should be determined, even afterthe current listening window has been extended, to maintain thesynchronization between the MS and BS.

FIG. 5 is a diagram illustrating operation of a wireless node in a casewhere the extension (m) of the current listening window is less than theinitial sleep window size (t). A number of listening windows (510, 514,518 and 522) and sleep windows (512 m 516 m 520 and 524) are shown inFIG. 5, with each window being one or more frames in length. A firstlistening window 510 has an unextended length (v) of 1 frame. Sleepwindow 512 has an initial sleep window size (t) of three (3) frames.

Next, traffic is exchanged between the MS and BS during listening window514, which causes the listening window 514 to be extended by m frames,where m is the extension of the current listening window. In thisexample, the extension (m) of the current listening window 514 is 1frame, which is less than the initial sleep window size (t) which is 3frames. Thus, m<t in the example shown in FIG. 5. The length of the nextsleep window 516 would normally be 3 frames, but it is reduced to t−mdue to the extension m of the listening window 514, according to thisexample. Thus, sleep window 516 has a length of 2 frames in the exampleshown in FIG. 5. The next listening window 518 starts at frame n+v+t,where n is the starting point of the current listening window 514, v isthe unextended length of a listening window, which is 1 frame in thisexample, and t is the initial sleep window size, which is 3 frames inthis example. Thus, n is at the beginning of listening window 514, v=1,and t=3, and v+t=4. Therefore, the starting point of the next listeningwindow 518 is 4 frames after the beginning of listening window 514,according to this example.

In general, the following equations may be used:

Length of the next sleep window=(k+1)*t−m (Eqn. 1), where m is theextension of the current listening window, t is the initial sleep windowsize, and k is a non-negative (zero or greater) integer based on thefollowing:k*t≦m<(k+1)*t.  (Eqn. 2)

The starting location of the next listening window=n+v+(k+1)*t (Eqn. 3),where n is the starting point of the current listening window, v is thelength of an unextended listening window, m is an extension of thecurrent listening window, and k is a non-negative integer (zero orgreater) provided by Eqn. 2.

For the case where m<t, from Eqn. 2, it can be shown that k=0. Thus,Eqn. 1 simplifies, for m<t, to: Length of the next sleep window=t−m(Eqn. 1A). Also, Eqn. 3 simplifies to: The starting location of the nextlistening window=n+v+t (Eqn. 3A).

Thus, as shown in FIG. 5, which illustrates flexibly extending oflistening window, there is traffic during listening window 514, and thelistening window 514 is extended by m=1 frame. The length of the nextsleep window 516=t−m=3−1=2 frames.

If there is no traffic in the next listening window 518, then the nextsleep window 520 will be doubled based on the size of t, e.g., 2t (sizeof 6 frames, since t=3 in this example), and next sleep windows may bedoubled in length if no traffic in their prior listening windows, e.g.,4t, 8t, etc., up to a maximum sleep window size. Sleep window 520 has alength of 2t which is 6 frames. Listening window 522 is not extended,and therefore, is a length of 1 frame. Each sleep window may be reset tothe initial sleep window size if there is traffic in the previouslistening window (but this reset length may be adjusted if the previouslistening window is extended, as noted above).

FIG. 6 is a diagram illustrating operation of a wireless node in a casewhere the extension (m) of the current listening window is greater thanor equal to the initial sleep window size (t): m≧t. Listening windows(610, 614, and 618) and sleep windows (612, 616 and 620) are shown inFIG. 6. In such case, where m≧t, k is a positive integer (1 or greater).Unextended listen window length (v) is 1 frame (see listening window610). Initial sleep window size (t)=3 frames, see sleep window 612.Traffic is exchanged during listening window 614, which causes listeningwindow 614 to be extended by m=t+1=4 frames. The next sleep window 616is reset to 3, but the length is reduced due to the extension oflistening window 614. The length of sleep window 616 is reduced tot−(m−t)=t−1=2 frames. The next listening window 618 starts at framen+v+2*t. The length of the following sleep windows may be doubled basedon the initial sleep window size (t), if the previous listening windowhas no MS/BS traffic exchanged. The next listening window 618 and sleepwindow 616 are shifted k*t frames as compared to the m<t case shown inFIG. 5.

According to an example embodiment, a technique is provided fordetermining a starting location of a next listening window for a mobilestation in a wireless network may include: communicating traffic betweenthe mobile station and a base station during a current listening window;determining, based on the communicating, an extension (m) of the currentlistening window; determining a length of a next sleep window based onthe extension (m) of the current listening window and an initial sleepwindow size (t); and determining a starting location of the nextlistening window based on the starting point (n) of the currentlistening window, a length (v) of an unextended listening window, theextension (m) of the current listening window and the initial sleepwindow size (t).

In an example embodiment, the determining a length of a next sleepwindow based on the extension (m) of the current listening window andthe initial sleep window size (t) may include determining the length ofthe next sleep window based approximately on the following: Length ofnext sleep window=(k+1)*t−m, where m is the extension of the currentlistening window, t is the initial sleep window size, and k is aninteger based on the following: k*t≦m<(k+1)*t.

In another example embodiment, the determining a starting location ofthe next listening window based on the starting point (n) of the currentlistening window, a length (v) of an unextended listening window, theextension (m) of the current listening window and the initial sleepwindow size (t) may include determining the starting location of thenext listening window based approximately on the following: Startinglocation of the next listening window=n+v+(k+1)*t, where n is thestarting point of the current listening window, v is the length of anunextended listening window, m is an extension of the current listeningwindow, and k is a positive integer provided by the following:k*t≦m<(k+1)*t.

FIG. 7 is a flow chart illustrating operation of a base stationaccording to an example embodiment. Operation 710 may includetransmitting a scheduling information to a mobile station in a wirelessnetwork during a listening window. Operation 720 may include determiningwhether an acknowledgement has been received within the listening windowfrom the mobile station that acknowledges receipt of the schedulinginformation. Operation 730 may include resetting a size of a next sleepwindow for the mobile station to an initial sleep window size if theacknowledgement has been received from the mobile station. And,operation 740 may include increasing a size of the next sleep window forthe mobile station if the acknowledgement has not been received from themobile station within the listening window.

In the flow chart of FIG. 7, the scheduling information may include ascheduling assignment, a Map message or other resource allocation toassign or allocate resources to the mobile station for either uplink ordownlink transmission.

In the flow chart of FIG. 7, the transmitting operation 710 may includetransmitting a scheduling assignment via a unicast service controlchannel to assign or allocate resources to the mobile station for eitheruplink or downlink data transmission.

In the flow chart of FIG. 7, the transmitting operation 710 may includetransmitting a scheduling assignment to the mobile station via anon-HARQ (non-Hybrid ARQ) transmission.

In the flow chart of FIG. 7, the transmitting operation 710 may includetransmitting a scheduling information to a mobile station in a wirelessnetwork, the scheduling information including a scheduling informationto allocate or schedule a downlink transmission to the mobile stationand to allocate uplink resources for the mobile station to transmit theacknowledgement that acknowledges receipt of the scheduling information.

In the flow chart of FIG. 7, the transmitting operation 710 may includetransmitting a scheduling information to a mobile station in a wirelessnetwork, the scheduling information including a first schedulinginformation to allocate resources for a downlink transmission to themobile station.

In the flow chart of FIG. 7, the transmitting operation 710 may includetransmitting a scheduling information to a mobile station in a wirelessnetwork, the scheduling information including a scheduling informationto allocate resources for a mobile station; and repeating, one or moretimes, the transmitting of the scheduling information if anacknowledgement is not received from the mobile station within a timeoutperiod, until either the end of the listening window is reached or anacknowledgement from the mobile station is received.

In the flow chart of FIG. 7, the increasing operation 740 may includedoubling a size of the next sleep window for the mobile station if theacknowledgement has not been received from the mobile station within thelistening window.

According to another example embodiment, an apparatus may include awireless transceiver; and a controller coupled to the transceiver. Thewireless transceiver may be configured to transmit a schedulinginformation to a mobile station in a wireless network during a listeningwindow. The controller may be configured to determine whether anacknowledgement has been received within the listening window from themobile station that acknowledges receipt of the scheduling information,reset a size of a next sleep window for the mobile station to an initialsleep window size if the acknowledgement has been received from themobile station, and increase a size of the next sleep window for themobile station if the acknowledgement has not been received from themobile station within the listening window.

FIG. 8 is a flow chart illustrating operation of a base stationaccording to an example embodiment. Operation 810 may includetransmitting a scheduling information to a mobile station in a wirelessnetwork during a listening window. Operation 820 may include determiningthat an acknowledgement has been received within the listening windowfrom the mobile station that acknowledges receipt of the schedulinginformation. And, operation 830 may include resetting a size of a nextsleep window for the mobile station to an initial sleep window sizebased on the receipt of the acknowledgement.

According to another example embodiment, an apparatus may include awireless transceiver and a controller coupled to the transceiver. Thewireless transceiver may be configured to transmit a schedulinginformation to a mobile station in a wireless network during a listeningwindow. The controller may be configured to: determine that anacknowledgement has been received within the listening window from themobile station that acknowledges receipt of the scheduling information,and reset a size of a next sleep window for the mobile station to aninitial sleep window size based on the receipt of the acknowledgement.

FIG. 9 is a flow chart illustrating operation of a mobile stationaccording to an example embodiment. Operation 910 may include receiving,at a mobile station from a base station in a wireless network during alistening window, a scheduling information that assigns or allocatesresources to the mobile station for either uplink or downlinktransmission. Operation 920 may include transmitting, within thelistening window, an acknowledgement from the mobile station thatacknowledges receipt of the scheduling information. Operation 930 mayinclude resetting a size of a next sleep window for the mobile stationto an initial sleep window size based on the receipt of the schedulinginformation for the mobile station.

FIG. 10 is a flow chart illustrating operation of a wireless nodeaccording to an example embodiment. The flow chart of FIG. 10 mayillustrate determining a starting location of a next listening windowfor a mobile station in a wireless network. Operation 1010 may includecommunicating traffic between the mobile station and a base stationduring a current listening window. Operation 1020 may includedetermining, based on the communicating, an extension (m) of the currentlistening window. Operation 1030 may include determining a length of anext sleep window based on the extension (m) of the current listeningwindow and an initial sleep window size (t). And, operation 1040 mayinclude determining a starting location of the next listening windowbased on the starting point (n) of the current listening window, alength (v) of an unextended listening window, the extension (m) of thecurrent listening window and the initial sleep window size (t).

In an example embodiment, operation 1020 may include determining, basedon the communicating, an extension (m) of the current listening window,where the listening window extension (m) is greater than or equal to theinitial sleep window size (t).

In an example embodiment, operation 1020 may include determining, basedon the communicating, an extension (m) of the current listening window,where the listening window extension (m) is less than the initial sleepwindow size (t).

In an example embodiment, operation 1010 may include transmitting and/orreceiving either scheduling information and/or data during a currentlistening window.

In an example embodiment, operation 1010 may include transmitting, fromthe base station, scheduling information that assigns or schedulesresources for the mobile station for at least one subframe of thecurrent listening window.

In an example embodiment, operation 1010 may include receiving, at themobile station from the base station, scheduling information thatassigns or schedules resources for the mobile station for at least onesubframe of the current listening window.

In an example embodiment, in the flow chart of FIG. 10, the currentlistening window is flexibly extended by the extension (m) based on anamount of traffic communicated between the base station and mobilestation during the current listening window.

In an example embodiment, operation 1030 may include determining thelength of the next sleep window based approximately on the following:

Length of next sleep window=(k+1)*t−m, where m is the extension of thecurrent listening window, t is the initial sleep window size, and k isan integer based on the following: k*t≦m<(k+1)*t.

In an example embodiment, operation 1040 may include determining thestarting location of the next listening window based approximately onthe following: Starting location of the next listeningwindow=n+v+(k+1)*t, where n is the starting point of the currentlistening window, v is the length of an unextended listening window, mis an extension of the current listening window, and k is a positiveinteger provided by the following: k*t≦m<(k+1)*t.

In another example embodiment, an apparatus may include a wirelesstransceiver, and a controller coupled to the transceiver. The wirelesstransceiver may be configured to transmit or receive traffic during acurrent listening window. And, the controller may be configured todetermine an extension (m) of the current listening window; determine alength of a next sleep window based on the extension (m) of the currentlistening window and an initial sleep window size (t); and determine astarting location of the next listening window based on the startingpoint (n) of the current listening window, a length (v) of an unextendedlistening window, the extension (m) of the current listening window andthe initial sleep window size (t).

In an example embodiment, the listening window extension (m) may begreater than or equal to the initial sleep window size (t).

In an example embodiment, the listening window extension (m) may be lessthan the initial sleep window size (t).

FIG. 11 is a flow chart illustrating operation of a mobile stationaccording to an example embodiment. The flow chart of FIG. 11 mayinclude a method of determining a starting location of a next listeningwindow for a mobile station in a wireless network. Operation 1110 mayinclude receiving, from a base station, traffic at the mobile stationduring a current listening window. Operation 1120 may includedetermining, based on the receiving, an extension (m) of the currentlistening window. And, operation 1130 may include determining a startinglocation of the next listening window based on the starting point (n) ofthe current listening window, a length (v) of an unextended listeningwindow, the extension (m) of the current listening window and theinitial sleep window size (t).

Operation 1120 may include receiving a message from the base stationthat identifies the extension (m).

Operation 1110 may include receiving, from a base station, schedulinginformation that assigns or allocates resources to the mobile stationfor either uplink or downlink transmission.

Operation 1110 may include receiving, from a base station, a firstscheduling information provided in a first subframe that assigns orallocates resources to the mobile station for downlink transmission tothe mobile station, and a second scheduling information that assigns orallocates uplink resources for the mobile station to transmit to thebase station an acknowledgement that acknowledges the mobile stationreceiving the first scheduling information.

In an example embodiment of the flow chart of FIG. 11, the traffic mayinclude at least a resource allocation or scheduling assignment thatassigns or allocates to the mobile station either uplink or downlinkresources. The flow chart may include one or more additional operations,including transmitting to the base station an acknowledgement toreceiving the resource allocation.

According to an example embodiment, an apparatus may include a wirelesstransceiver and a controller coupled to the transceiver. The wirelesstransceiver may be configured to receive, from a base station, trafficat the mobile station during a current listening window. The controllermay be configured to determine an extension (m) of the current listeningwindow; and determine a starting location of the next listening windowbased on the starting point (n) of the current listening window, alength (v) of an unextended listening window, the extension (m) of thecurrent listening window and the initial sleep window size (t).

In an example embodiment, the listening window extension (m) may begreater than or equal to the initial sleep window size (t).

FIG. 12 is a block diagram of a wireless station (or wireless node) 1200according to an example embodiment. The wireless station 1200 (e.g. basestation 104 or mobile node 106, 108, 110) may include, for example, awireless transceiver (or wireless interface) 1202, including atransmitter to transmit signals and a receiver to receive signals, acontroller 1204 to control operation of the station and executeinstructions or software, and a memory 1206 to store data and/orinstructions. Controller 1204 may also make decisions or determinations,generate frames or messages for transmission, decode received frames ormessages for further processing, and other tasks or functions describedherein.

Controller 1204 may be programmable and capable of executing software orother instructions stored in memory or on other computer media toperform the various tasks and functions described above, such as one ormore of the tasks or methods described above.

In addition, a storage medium may be provided that includes storedinstructions, which when executed by a controller or processor mayresult in the controller 1204, or other controller or processor,performing one or more of the functions or tasks described above.

Implementations of the various techniques described herein may beimplemented in digital electronic circuitry, or in computer hardware,firmware, software, or in combinations of them. Implementations mayimplemented as a computer program product, i.e., a computer programtangibly embodied in an information carrier, e.g., in a machine-readablestorage device or in a propagated signal, for execution by, or tocontrol the operation of, a data processing apparatus, e.g., aprogrammable processor, a computer, or multiple computers. A computerprogram, such as the computer program(s) described above, can be writtenin any form of programming language, including compiled or interpretedlanguages, and can be deployed in any form, including as a stand-aloneprogram or as a module, component, subroutine, or other unit suitablefor use in a computing environment. A computer program can be deployedto be executed on one computer or on multiple computers at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

Method steps may be performed by one or more programmable processorsexecuting a computer program to perform functions by operating on inputdata and generating output. Method steps also may be performed by, andan apparatus may be implemented as, special purpose logic circuitry,e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. Elements of a computer may include atleast one processor for executing instructions and one or more memorydevices for storing instructions and data. Generally, a computer alsomay include, or be operatively coupled to receive data from or transferdata to, or both, one or more mass storage devices for storing data,e.g., magnetic, magneto-optical disks, or optical disks. Informationcarriers suitable for embodying computer program instructions and datainclude all forms of non-volatile memory, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor andthe memory may be supplemented by, or incorporated in, special purposelogic circuitry.

To provide for interaction with a user, implementations may beimplemented on a computer having a display device, e.g., a cathode raytube (CRT) or liquid crystal display (LCD) monitor, for displayinginformation to the user and a keyboard and a pointing device, e.g., amouse or a trackball, by which the user can provide input to thecomputer. Other kinds of devices can be used to provide for interactionwith a user as well; for example, feedback provided to the user can beany form of sensory feedback, e.g., visual feedback, auditory feedback,or tactile feedback; and input from the user can be received in anyform, including acoustic, speech, or tactile input.

Implementations may be implemented in a computing system that includes aback-end component, e.g., as a data server, or that includes amiddleware component, e.g., an application server, or that includes afront-end component, e.g., a client computer having a graphical userinterface or a Web browser through which a user can interact with animplementation, or any combination of such back-end, middleware, orfront-end components. Components may be interconnected by any form ormedium of digital data communication, e.g., a communication network.Examples of communication networks include a local area network (LAN)and a wide area network (WAN), e.g., the Internet.

While certain features of the described implementations have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the various embodiments.

What is claimed is:
 1. A method comprising: transmitting a schedulinginformation to a mobile station in a wireless network during a listeningwindow; determining whether an acknowledgement has been received withinthe listening window from the mobile station that acknowledges receiptof the scheduling information; resetting a size of a next sleep windowfor the mobile station to an initial sleep window size if theacknowledgement has been received from the mobile station; andincreasing a size of the next sleep window for the mobile station if theacknowledgement has not been received from the mobile station within thelistening window.
 2. The method of claim 1 wherein the schedulinginformation comprises a scheduling assignment, a Map message or otherresource allocation to assign or allocate resources to the mobilestation for either uplink or downlink transmission.
 3. The method ofclaim 1 wherein the transmitting comprises transmitting a schedulingassignment via a unicast service control channel to assign or allocateresources to the mobile station for either uplink or downlink datatransmission.
 4. The method of claim 1 wherein the transmittingcomprises transmitting a scheduling information to a mobile station in awireless network, the scheduling information including a schedulinginformation to allocate or schedule a downlink transmission to themobile station and to allocate uplink resources for the mobile stationto transmit the acknowledgement that acknowledges receipt of thescheduling information.
 5. The method of claim 1 wherein thetransmitting comprises transmitting a scheduling information to a mobilestation in a wireless network, the scheduling information including afirst scheduling information to allocate resources for a downlinktransmission to the mobile station.
 6. The method of claim 1 wherein thetransmitting comprises: transmitting a scheduling information to amobile station in a wireless network, the scheduling informationincluding a scheduling information to allocate resources for a mobilestation; and repeating, one or more times, the transmitting of thescheduling information if an acknowledgement is not received from themobile station within a timeout period, until either the end of thelistening window is reached or an acknowledgement from the mobilestation is received.
 7. The method of claim 1 wherein the increasingcomprises doubling a size of the next sleep window for the mobilestation if the acknowledgement has not been received from the mobilestation within the listening window.
 8. An apparatus comprising: awireless transceiver; a controller coupled to the transceiver; thewireless transceiver configured to transmit a scheduling information toa mobile station in a wireless network during a listening window; thecontroller configured to: determine whether an acknowledgement has beenreceived within the listening window from the mobile station thatacknowledges receipt of the scheduling information; reset a size of anext sleep window for the mobile station to an initial sleep window sizeif the acknowledgement has been received from the mobile station; andincrease a size of the next sleep window for the mobile station if theacknowledgement has not been received from the mobile station within thelistening window.
 9. An apparatus comprising: a wireless transceiver; acontroller coupled to the transceiver; the wireless transceiverconfigured to transmit a scheduling information to a mobile station in awireless network during a listening window; the controller configuredto: determine that an acknowledgement has been received within thelistening window from the mobile station that acknowledges receipt ofthe scheduling information; and reset a size of a next sleep window forthe mobile station to an initial sleep window size based on the receiptof the acknowledgement.
 10. A method comprising: receiving, at a mobilestation from a base station in a wireless network during a listeningwindow, a scheduling information that assigns or allocates resources tothe mobile station for either uplink or downlink transmission;transmitting, within the listening window, an acknowledgement from themobile station that acknowledges receipt of the scheduling information;and resetting a size of a next sleep window for the mobile station to aninitial sleep window size based on the receipt of the schedulinginformation for the mobile station.